Cylindrical light emitter

ABSTRACT

In combination; an inner transparent cylinder of high compression strength and thermal shock resistant material having an inner bore space; an active material capable of lasering disposed within said inner bore space; a diffusing outer cylinder capable of withstanding tension shock concentrically disposed to said first cylinder and forming a first annular space thereinbetween of 2 to 12 millimeters; an end member, including an electrode portion, disposed at each end of said cylinders and enclosing said first annular space at each end thereof; each said end member having an inner annular recession; the walls of said recession defining a second annular space with the exterior of said inner cylinder to provide an expansion chamber at each end of said first annular space; means for providing gas to said annular spaces; and means for energizing said electrode portions to ionize the gas within said annular spaces.

United States Patent [72] Inventors Charles H. Church; OTHER REFERENCESEflward Amon' both w'lkmsburg Colgate et al.. The Dynamic Pinch as aHigh-Intensity msburflhi Light Source for Optical Maser Pumping."ADVANCES IN PP" 600,188 QUANTUM ELECTRONICS; J. R. Singer, 5a.; ColumbiaFlled University Press, New York, N.Y.; pp. 288- 292 (1961). [45]Patented June 15, 1971 [73) Assignee Westinghouse Electric Corporation f'f L sflfes pmsburgh, pm Assistant Examiner-William L. Slkesconfinuafiommpm f application Nm Att0rneys-F. H. Henson and E. P.Klipfel 272,678, Apr. 12, 1963, now abandoned.

ABSTRACT: in combination; an inner transparent cylinder of highcompression strength and thermal shock resistant material having aninner bore space; an active material capable of lasering disposed withinsaid inner bore space; a diffusing [54] CYLINDRICAL LIGHT EMITTER outercylinder capable of withstanding tension shock concentrically disposedto said first cylinder and forming a first annu- 5 Claims, 3 DrawingFigs.

lar space therembetween of 2 to 12 millimeters; an end [52] U.S. Cl331/945, member, includin an electrode portion, dis osed at each end S P313/217 of said cylinders and enclosing said first annular space at eachend thereof; each aid end member having an inner annular [50] Field ofSearch 331/945; recession; the walls f Said recession d fi i a secondannular 330/43; 313/217, 7 space with the exterior of said innercylinder to provide an expansion chamber at each end of said firstannular space; [56] References Cited means for providing gas to saidannular spaces; and means for UNITED STATES PATENTS energizing saidelectrode portions to ionize the gas within said 3,209,281 9/1965Colgate et a1 331/945 annular spaces.

I \x I m W Q4 a 4 6 MW M CYLINDRICAL LIGHT EMITTER This application is acontinuation-in-part of US. Pat. application Ser. No. 272,678, filedApr. 12, 1963, now abandoned.

The present invention relates generally to cylindrical light emittersand more particularly relates to a cylindrical emitter of light for thepurpose of pumping a laser.

Cylindrical flash sources for pumping an active material capable oflasering have been unable to provide sufficient light output and stillwithstand the shock resulting from the firing of the gas containedtherein. For many applications of lasers, there is a requirement for avery high energy rate pump which is capable of high total energies atrelatively high efficiencies. Conventional light sources are unable toprovide for sufficient current density. The shock wave which occurs in apulsed flashlamp tends to destroy the arch container.

Briefly, the present invention provides a cylindrical emitter of light,the construction of which provides both mechanical and opticaladvantages. The mechanical advantages stem from having a mechanicallystrong outer cylinder to withstand both the radial and longitudinalstresses due to the high pressure and temperature buildup. At the sametime, the active material capable of l'asering is optically coupled to adiffuse reflector in very close proximity to the active material. Byproviding a relatively thin annular space filled with gas the currentdensity is greatly increased thereby allowing greater light output. Theconstruction of an expansion chamber within the cylindrical lamp allowsthe shock wave which occurs in pulsed flashlamps to be absorbed withoutdestroying the lamp.

Accordingly, an object of the present invention is to provide a new andimproved cylindrical emitter of light.

Another object of the present invention is to provide a cylindricalemitter of light capable of intensity outputs heretofore unattainable.

Another object of the present invention is to provide an emitter oflight capable of efficiently pumping an active material in the laserpumping light bands.

Further objects and advantages of the present invention will be readilyapparent from the following detailed description taken in conjunctionwith the drawing, in which:

FIG. 1 is a cross-sectional elevational view taken along the line [-1 ofFIG. 2 of an illustrative embodiment of the present invention;

FIG. 2 is an end elevational view of the illustrative embodiment; and,

FIG. 3 is a schematic representation of a system utilizing theillustrative embodiment shown in the previous figures.

Referring to FIG. I, an active material 2 capable of lasering isillustrated disposed within an inner cylindrical member 4 having highcompressive strength and which is transparent. The inner cylinder 4 isconventionally made of quartz or other high temperature and thermalshock resistant similar material. An outer cylinder 6 is concentricallydisposed to said inner cylinder 4 and forms an annular space 8thereinbetween. End members 10 and 12 are respectively disposed atopposite ends of the cylinders 4 and 6 and enclose the annular space 8.A thermal and shock resistant adhesive 14 secures the end members l and12 to the cylindrical members 4 and 6. As illustrated, the end membersand 12 may be of suitable metal to function as electrodes across theannular space 8. Otherwise, any other suitable material for electrodesmay be inserted into the end members 10 and 12. A passageway 16 throughthe end members 12 provides access for evacuation and filling of theannular space 8 with a suitable gas to be excited upon an ionizingpotential being impressed upon the electrode end members 10 and 12.

For optimum optical pumping of the laser material 2 it is necessary tohave extremely high current densities with a fast rise time. Towardsthis end the cylindrical construction of the present invention allows avery low impedance device. It is, in essence, many linear tubes allconnected in parallel. The use of the straight line tube lowers thevalue of inductance and also eliminates any magnetic field effects whichdo occur when a conventional helical emitter configuration is usedaround the laser rod. The inner diameter of the outer cylinder 6 isselected to be displaced from the inner cylinder 4 by a very smalldistance; that is, in the order of several millimeters such as 2 to 12mm. If the annular space is made too thin then not enough emitters areavailable for providing a proper light intensity but on the other hand,should the annular spacebe made too large than too much absorptionoccurs for the most efficient light output.

To improve the optical coupling the inner surface of the outer cylinder6 is provided with a diffusing surface. A material such as alumina isused since it is more able to withstand the tension shock which resultsupon the outer cylinder 6 when the arc is struck in the annular space 8.Where necessary, an epoxy bound glass filament structure may be woundaround the outer cylinder 6 to provide the cylinder 6 withprecompression thereby improving the elastic properties of the aluminaupon occurrence of a shock wave within the annular space 8.

To improve the spectral output of the light emitted from the source 2the pumping media or gas, which could be xenon or another rare gas at aproper pressure, may have other materials such as mercury or themetallic halides added to the arc discharge plasma. The addition ofselective emitting materials possessing strong emission lines to thecylindrical tube 2 yields a system having the advantages of higherresistance and selective emission when compared to the conventionalarrangements. It has been found however that such additives in manyinstances condense in a cooler portion of the tube 2 after firing,thereby not being available to be excited for the next pulse. In suchinstances, the desirable additives may be incorporated in the electrodematerial which does not get very not and is not subject to the extremetemperatures during discharge. Since the amount of additive required inthe arc is small, the quantity need not be so large as to interfere withthe diffuse reflectivity of the outer ring 6.

Referring again to FIGS. 1 and 2 when an ionizing potential is appliedto the end members 10 and 1 2 the shoulder portions 20 provide thetenninal areas for the electric arc struck in the annular space.Immediately behind the terminal areas is located a larger annular spaceor expansion chamber 22 wherein the shock occurring upon the firing ofthe lamp 2 may be absorbed. At the same time, the thermal and shockresistant adhesive 14 is capable of flexing with the shock wave tominimize rupturing of the construction.

In operation, it can readily be seen from FIG. 3 that the end members 10and 12 are connected across an ionizing potential by means of a gangoperated switch 30. The switch 30 connects a power supply, illustratedto be of four capacitors 32, across the electrode end members 10 and 12discharging thereacross and thereby ionizing the gas within the annularspace 8.

While the present invention has been described with a degree ofparticularity for the purposes of illustration, it is to be understoodthat all equivalents, modifications and alterations within the spiritand scope of the present invention are herein meant to be included.

What we claim is:

1. In combination; an inner transparent cylinder of high compressionstrength and thermal shock resistant material having an inner borespace; an active material capable of lasering disposed within said innerbore space; a diffusing outer cylinder capable of withstanding tensionshock concentrically disposed to said first cylinder and forming a firstannular space thereinbetween of 2 to 12 millimeters; an end member,including an electrode portion, disposed at each end of said cylindersand enclosing said first annular space at each end thereof; each saidend member having an inner annular recession; the walls of saidrecession defining a second annular space with the exterior of saidinner cylinder to provide an expansion chamber at each end of said firstannular space; means for providing gas to said annular spaces; and meansfor energizing said electrode portions to ionize the gas within saidannular spaces.

2. A flashlamp structure which comprises: an inner elongated tubularmember, an outer elongated tubular member surrounding said inner membercoaxial therewith with an annular space therebetween selected to bewithin the range of 2 to 12 millimeters, end electrodes surrounding aportion of said inner tubular member and the ends of said outer tubularmember, means associated with said end electrodes for vacuum sealing thespace confined between said inner and outer tubular members by said endelectrodes, and means through which said lamp may be evacuated and a gas

1. In combination; an inner transparent cylinder of high compressionstrength and thermal shock resistant material having an inner borespace; an active material capable of lasering disposed within said innerbore space; a diffusing outer cylinder capable of withstanding tensionshock concentrically disposed to said first cylinder and forming a firstannular space thereinbetween of 2 to 12 millimeters; an end member,including an electrode portion, disposed at each end of said cylindersand enclosing said first annular space at each end thereof; each saidend member having an inner annular recession; the walls of saidrecession defining a second annular space with the exterior of saidinner cylinder to provide an expansion chamber at each end of said firstannular space; means for providing gas to said annular spaces; and meansfor energizing said electrode portions to ionize the gas within saidannular spaces.
 2. A flashlamp structure which comprises: an innerelongated tubular member, an outer elongated tubular member surroundingsaid inner member coaxial therewith with an annular space therebetweenselected to be within the range of 2 to 12 millimeters, end electrodessurrounding a portion of said inner tubular member and the ends of saidouter tubular member, means associated with said end electrodes forvacuum sealing the space confined between said inner and outer tubularmembers by said end electrodes, and means through which said lamp may beevacuated and a gas admitted into the spacing between said inner andouter tubular members.
 3. A flashlamp structure as claimed in claim 2,which includes: a light reflective means around the midsection of saidouter tubular member.
 4. A flashlamp as claimed in claim 3, in which:said light reflective means is coated on the inner surface of said outertubular member.
 5. A flashlamp structure as claimed in claim 2 includingan epoxy bound glass filament means wound around said outer elongatedtubular member to protect said flashlamp structure against internalshock waves.